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Oct. 30 1923. 1,4723%? w. W. KEMP METHOD OF AND APPARATUS FOR CASE HARDENING Filed Nov. '7, 1921 lm uemfivr; wzjmazn 6% 0,

Patented Oct. 30, 1923.

UNITED STATES that? PATE'l FFIQE WILLIAM WALLACE KEMP, 0F BALTIMORE, MARYLAND, ASSIGNOR OF ONE-HALF TO WILLIAM H. VAE'l' HORN, OF BALTIMORE, MARYLAND.

METHOD OF AND APPARATUS FOR CASE HARDENING.

Application filed November '7, 1921. Serial No. 513,443.

To all whom it may concern:

Be it known that l, VVILLIAM lVALLAon KEMP, a citizen of the United States, residing at Baltimore, in the county of Baltimore City and State of Maryland, have invented new and useful Improvements in Methods of and Apparatus for Case Hardening, of which the following is a specification.

The present invention relates to a method of and apparatus for case hardening, and has for its object to provide for the treatment of articles by means of any suitable carbonizing agent at the same time that they are being subjected to the direct heating action of a flame.

Various methods for case hardening have been heretofore proposed. Under one method therehas been proposed placing articles to be hardened in a retort together with a suitable carbonizing agent, and subjecting that retort to external heating to bring the articles to the proper temperature to take up the carbonizing medium. Another method has been to first heat the articles in a proper container by direct heat until they are brought to the desired temperaturaand then either removing them from the container and bringing them into the presence of the carbonizing agent, or to extinguish the heating flame and then introduce the carbonizing material into the presence of the heated articles.

Both of these methods are objectionable the first for the reason that where the articles and the carbonizing agent are placed in the retort and. the retort is subjected to external heat, the retorts tend to breakdown from the excessive heat required to bring the interior of the retort to the proper temperature, and, furthermore, the operation of loading the retort with the articles to be hardened and introducing the hardening agents is cumbersome and expensive, The operation of directly heating the articles, then removing them from the action of the heating agent into the presence of a carbonizing medium; or extinguishing the flame, and introducing the carbonizing agent, is slow and tedious.

A serious objection to both of the methods above set forth is that it is difficult to maintain the articles at a uniform heat. which is "very essential "thing, order that when the articles have been brought to a proper temperature, they may be maintained at that temperature during the action of the carbonizing agent.

My method and apparatus contemplate the internal firing of a retort and the heating of the articles contained therein in the presence of the carbonizing agent, this bemg accomplished by the use of a self-sustaining fuel which will burn in the presence of the carbonizing agent without any danger of ignition and burning of that carbonizing agent. Following my method and utilizing my apparatus, it is possible to maintain, in a closed retort, a heating flame or jet which will bring the articles to and maintain them at a proper and uniform temperature for case hardening; and, at the same time, introduce into the retort the case hardening agent without any danger of smothering the heating flame or igniting the carbonizing element.

In order that the invention may be clear tothose skilled in the art, I have shown, in the accompanying drawings, one physical embodiment of my invention, but it will be understood that this disclosure is merely illustrative and in'no sense restrictive of the invention, as apparatus other than that shown in the drawings, may, of course, be used in practicing my method.

In the drawings Figure 1 isa View in side elevation of a retort by which my method may be practiced.

Figure 2 is a longitudinal section of the retort shown in Figure 1.

Referring to the drawings by numbers, like numbers indicating like parts in the several views, 10 indicates retort of any suitable construction and design, it being here shown as a cylindrical metal container lined, if desired, with refractory material, conventionally shown. Said retort is provided with a door 11, which is so fashioned that it may be tightly closed so that the retort 10 will be substantially closed against the entrance of atmospheric air. Mounted within the retort 10 is a cageor rattler 12 which will be provided with a door 13 to provide a loading opening. The cage 12 has a foraminous wall, as shown, and is preferably mounted for revolution on gudgeons 14, passing through stuffing boxes 15 in the ends of the retort 10, suitable means (not shown) being provided for rtating the cage 12 which receives the articles to be case hardened.

The retort is provided at suitable points, preferably at one end, with one or more fuel pipes 16, four being shown in the present case, distributed circumferentially approximately 90 apart and delivering, preferably, outside of the circumferential area of the cage 12, so that the cage and the articles contained therein will be substantiially surrounded by the heating medium. The said pipe or pipes 16 deliver a mixture of fuel, preferably gaseous, to the closed retort 10, this fuel being preferably a mixture of gas and air in such proportions that it will be self-sustaining and will burn in the closed retort in the absence of air from any independent supply. I

There will, of course, be no air to support combustion in the retort 10, for the fuel delivered from the pipes 16 has an air content sufficient only to sustain combustion of the fuel, and not enough to permit ignition and burning of'the carbonizing agent. Atmospheric air cannot enter the retort 10 in suiiicient volume to support combustion, for with the closed retort 10, there'is no chance for ingress of air in any quantity, and the pressure within the retort will be such as to effectively overcome atmospheric pressure tending to force air into the retort.

This carbonizing agent, which may be either in granular, liquid, or gaseous form, may be introduced into the retort 10 in any suitable fashion, either when the retort is loaded, or, if desired, by providing feed pipe or opening delivering to the retort 10. Under this method, and with this arrangement, the articles to be case hardened may be simultaneously subjected to the heating and the carbonizing actions, so that they may be brought to any desired temperature and there maintained during the carbonizing process.

This method has the advantage over methods known to me of permitting the articles to be brought to the desired temperature and maintaining them uniformly at that temperature until penetration and hardening has progressed to the point desired, so that immediately the absorption temperature is reached, the case hardening begins and is continued without interruption, and there is no chance of variations in temperature of the articles during the treatment, which would result in imperfect such character that it will sustain combusf tionin the absence of ail Within. the closed" retort, the air content o f'the mixture being so proportioned as to accomplish this result, but that the carbonizing agent will not ignite for the reason that there is not, within the retort 10, which is substantially closed against the ingress of atmospheric air and within which is maintained a sufficient pressure to exclude the entrance of air, sufficient oxygen to sustain combustion. The danger of burning the carbonizing mixture is, therefore, eliminated. V

The retort 10 will preferably be provided with a bleeder 17 through which the waste gases will be forced by pressure within the retort, and these waste gases may be conducted away or burned at the orifice of the bleeder 17, as may be desired.

Under this method and utilizing this ap paratus, I have provided an economical and simple way of case hardening articles, eliminating the external firing method with the closed retort, now commonly in use, or-the somewhat cumbersome method of first firing and then subjecting the fired articles to the action of the carbonizing agent.

Such changes in the apparatus and new steps of the method as are within the skill of the mechanic may be made, without departing from the range of my invention.

- I claim:

1. The method of case hardening, which consists in enclosing the articles in a con tainer and heating them by combustion within the container in the presence of a carbonizing agent without igniting the carbon izing agent.

2. The method of case hardening, which consists in enclosing the articles in a container and heating them by a flame within the container in the presence of a carbonizing agent without igniting the carbonizing agent.-

3. The method of case hardening, which consists in enclosing the articles to be treated in a container, bringing the articles to a proper temperature by burning a selfsustaining fuel in said container, and subjecting the articles to the action of a carbonizing agent without igniting said cartreated in a container, bringing the articles to a proper temperatureby introducing a self-sustaining flame interiorlyof said container, and simultaneously subjecting the articles to the action of acarbonizing agent without igniting said carbonizing agent. i

5. The method of case hardening, which consists in enclosing the articles to be treated in a container, bringing the articles to a proper temperature by introducing a self-sustaining flame interiorly of said con tainer, agitating the articles, and subjecting them to the action of casehardening agent without igniting said carbonizing agent.

6. The method of case hardening, which consists in enclosing the articles to be treated and a suitable case hardening agent in a container, and bringing said articles to a proper temperature by introducing a selfsustaining flame into said container Without ignitin said carbonizing agent.

7. Apparatus for case hardening articles, comprising a. container adapted to receive the articles and a carbonizing agent, and means for introducing a combustible fuel into said container and burning it therein Without 'gniting the carbonizing agent.

8. Apparatus for case hardening articles, comprising a container adapted to receive the articles, a receptacle for the articles to be ha 'dened in said container, and means for introducing a self-sustaining flame into said container Without igniting the carbom izing agent.

9. Apparatus for case hardening articles, comprising a container adapted to receive the articles and a carbonizing agent, a receptacle for the articles to be hardened in said container, means foragitating the articles, and means for introducing a selfsustaining flame into said container Without igniting said carbonizing agent.

10. Apparatus "for case hardening articles, comprising a container adapted to receive the articles and a carbonizing agent, a foraminous receptacle for the articles to be hardened in said container, means for the articles, and means for introducing a self-sustaining flame into said container Without igniting said carbonizing agent.

11. Apparatus for case hardening articles, comprising a container adapted to receive the articles and a carbonizing agent, a movable receptacle for the articles to be hardened in said container, and means for introducing a self-sustaining flame into said container without igniting said carbonizing agent.

13. Apparatus for case hardening articles, comprising a stationary container adapted to receive the articles and a carbonizing agent having bearings at each end thereof, a foraminous receptacle for the articles to be hardened revolubly mounted in said bearings, and a burner delivering a selfsustaining flame interiorly of said fixed air-tight container Without igniting said carbonizing agent.

14. Apparatus for case har dcnlng articles, comprising a stationary container adapted to receive the articles and a carbonizing agent and having bearings at each end. thereof, a foraminous receptacle revolubl mounted in said bearings, and a plurality of burners delivering self-sustaining flames about said foraminous receptacle Without igniting said carbonizing agent.

15. Apparatus for case hardening articles, comprising a stationary container adapted to receive the articles and a carbonizing agent and having bearings at each end thereof, a foraminous receptacle revolubly mounted in said bearings, a plurality of burners delivering self-sustaining flames about said foraminous receptacle Without igniting said carbonizing agent, and a bleeder pipe delivering from said container.

In testimony whereof I have hereunto set my hand.

VVILLI'AM WALLACE KEMP. 

